Modern electronic circuits such as, for example, ASICs, FPGAs, and microprocessors, have a broad range of current demands ranging from very high peak currents to relatively low quiescent currents. Although switching regulators can be designed to be highly efficient over a moderate range of load currents, future generations of electronic circuits will probably demand higher maximum output currents and greater dynamic range from power supplies. The modern trends toward increasing numbers of board-level voltage supplies, lower voltages, and smaller circuit board sizes with increased cooling concerns tends to create a growing need to use point-of-load (POL) voltage converters (or as they are called in some embodiments, “voltage regulators”). Further, such trends also tend to create the need to incorporate highly responsive power management control functions within POL converters in order to satisfy load/line requirements.
A synchronous buck switching voltage regulator is a power supply circuit that attempts to provide an output current to a load at a predetermined output voltage. Typical synchronous buck regulators have certain inherent constraints that limit their ability to satisfy the increasing demands of contemporary microprocessors. For example, synchronous buck regulators typically employ series inductors that inhibit high frequency changes in output. Synchronous buck topologies also typically employ high power FETs controlled by circuit drivers. Such designs exhibit large input capacitances that limit switching rates.
Some previously known power supply strategies have coupled in parallel a plurality of switching regulator stages to deliver high output currents to a load such as a microprocessor. Typically, switching transistors are controlled to direct input current into only one regulator stage at a time. Duty ratios in these stages typically decrease as input voltages rise to minimize power plane current while output voltages drop to accommodate faster integrated circuitry and the associated increased derivatives of the power demand curve.
Many modern integrated circuits provide digital feedback signals that convey information about the circuit's power requirements to the power supply. The slow response of synchronous buck topologies and other power supply schemes may introduce instabilities in the feedback loop. Further, many contemporary microprocessors and ASICs turn on or off different parts of the integrated chip or system as needed to conserve power. This increases the demands on the voltage regulator to accommodate changes in load requirements.
What is needed, therefore, is a voltage converter with the ability to source current across a large dynamic range with high speed, stepping and control flexibility and the capability to supply multiple loads with a variety of voltages and currents while exhibiting fast current ramp-up and ramp-down capabilities, dynamic feed-forward and feedback configuration with high efficiency.